"Fat-Soluble Vitamin Interactions: An Ancestral Perspective."

The central theme will be that altogether too much focus has been placed on obtaining optimal serum 25(OH)D as a marker of vitamin D status, and while looking at 25(OH)D is useful, we need to shift the greater emphasis towards looking at interactions with other nutrients, especially vitamins A and K, both clinically and in research, a phenomenon that has been mostly neglected.

I will start out by critiquing what I call the "naked ape" hypothesis of optimal serum 25(OH)D concentrations, move on to question whether there is such a thing as an optimal 25(OH)D concentration, show why 25(OH)D is not a specific marker of vitamin D input despite being commonly used that way, and discuss numerous factors besides vitamin D that affect 25(OH)D.

This will include an argument that calcitriol should be measured together with 25(OH)D in order to provide more information.

I will then argue that the current trend to promote vitamin D supplementation, without adequate attention to vitamins A and K, and sometimes even coupled to recommendations to limit or decrease vitamin A intake, has the potential to promote pathological soft tissue calcification.

I will conclude by discussing the interactions among these vitamins and arguing that obtaining these vitamins together, as they would have occurred in ancestral diets, makes them most safe and effective.